In the future the machines will need spare parts and maintenance.这些机器将来会需要备件和维修保养。A technician loads a video tape into one of the machines.一名技师把一盒录影带装进其中一台机器。Many of the machines are gathering dust in basements.许多机器尘封在地下...
She was dancing while someone substituted at the piano.她在跳舞,别人代她弹钢琴.The synthesis methods of melatonin, related tryptaminetryptamine derivatives and substituted indoles are discussed.从人工合成的角度综述了美乐托宁及有关化合物色胺、色胺衍生物及吲哚衍生物的制...